1889.] Scpncntation of the Ovum. 767 
D the inner set is no longer separated into distinct cells, although 
there are a number of nuclei, each of which marks the centre of 
a future cell ; in such instances we must regard the whole inner 
portion as not yet transformed into a definite entodermic cell- 
layer. This figure is particularly instructive, because it shows 
that what we call the yolk is not something distinct from the 
germ, but really belongs to the inner layer of the embryo. E 
shows a similar &^o^ in which the outer set of cells has not yet 
grown around the yolk. F shows the same egg, not in section 
but seen from the outer surface. 
LIST OF AUTHORITIES CITED. 
Agassiz Alex, and Whitman, C. O. On the development of some pelagic fish-eggs. 
Preliminary notice, Proc. Am. Acad., XX., pp. 23-75, PI. I., 1884. 
Balfour, F. M. On the early development of Lacertilia, together with some observa- 
